1. Field of the Invention
The present invention relates generally to medical devices and methods. More particularly, the invention relates to apparatus and methods for independently delivering segmented stents or stent grafts within a body lumen.
Stenting has become an increasingly important treatment option for patients with coronary artery disease. Stenting involves the placement of a tubular prosthesis within a diseased coronary artery to expand the arterial lumen and maintain the patency of the artery. Early stent technology suffered from problems with restenosis, the tendency of the coronary artery to become re-occluded following stent placement. In recent years, however, improvements in stent design and the advent of drug-eluting stents have reduced restenosis rates dramatically. As a result, the number of stenting procedures being performed in the United States, Europe, and elsewhere has soared.
Stents are delivered to the coronary arteries using long, flexible vascular catheters, typically inserted through a femoral artery. For self-expanding stents, the stent is simply released from the delivery catheter, and it resiliently expands into engagement with the vessel wall. For balloon expandable stents, a balloon on the delivery catheter is expanded which expands and deforms the stent to the desired diameter, whereupon the balloon is deflated and removed.
Despite many recent advances in stent delivery technology, a number of shortcomings still exist. For example, current stent delivery catheters are not capable of customizing the length of the stent in situ to match the size of the lesion to be treated. While lesion size may be measured prior to stenting, using angiography or fluoroscopy, such measurements may be inexact. If a stent is introduced that is found to be of inappropriate size, the delivery catheter and stent must be removed from the patient and replaced with a different device of correct size. Moreover, current stent delivery devices cannot treat multiple lesions with a single catheter. If multiple lesions are to be treated, a new catheter and stent must be introduced for each lesion to be treated.
Additionally, currently available stent delivery devices are not well-adapted for treating vascular lesions that are very long and/or in curved regions of a vessel. Current stents have a discrete length that is relatively short due to their stiffness. If such stents were made longer, to treat longer lesions, they would not conform well to the curvature of vessels or to the movement of vessels on the surface of the beating heart. On the other hand, any attempt to place multiple stents end-to-end in longer lesions is hampered by the inability to maintain appropriate inter-stent spacing and to prevent overlap of adjacent stents. Such shortcomings in the prior art are addressed by the inventions described in U.S. patent application Ser. No. 10/412,714, entitled “Apparatus and Methods for Delivery of Multiple Distributed Stents,” filed on Apr. 10, 2003; and U.S. patent application Ser. No. 10/637,713, entitled “Apparatus and Methods for Delivery of Multiple Distributed Stents,” filed on Aug. 8, 2003; both applications assigned to the assignee of the present invention, and both applications being hereby incorporated fully by reference.
Even with improvements such as those described in the above-referenced patent applications, further improvements in stent delivery devices and methods are still being sought. For example, flexibility of a stent is important in stenting long lesions, tortuous vessels, lesions at vessel branches and the like. The above referenced patent applications disclose the use of segmented stents with separate or separable segments to provide highly flexible stents of selectable length. However, in some cases it may be advantageous to use segments that are coupled together during deployment to maintain segment alignment and prevent mobilization of the segments. It may also be beneficial to use interconnected stents to form a tubular passage, such as a graft.
As another example, many balloon-expandable stents are currently delivered by devices in which the stents are in direct contact with the balloon or other expandable member. If such stents are pushed or otherwise advanced along the expandable member in its deflated state, the direct contact between the stents and the balloon during advancement may cause damage to the balloon and/or to the stents or their coatings. A balloon or other expandable member may also interfere with stent advancement, especially after the balloon has been inflated and deflated multiple times and, thus, becomes somewhat flaccid and/or deformed. Thus, stent delivery devices in which the stents directly contact the expandable member may lead to increased risk of balloon or stent damage, increased general wear and tear, difficult stent advancement along the delivery device, and less precise stent placement.
Therefore, a need exists for improved stent delivery devices and methods. Ideally, such devices and methods would provide flexible coupling of stent segments during deployment of the segments. Also ideally, such devices and methods would at least reduce direct contact between stents and the expandable member of the delivery device to reduce damage to the stents and expandable member and to facilitate stent placement. At least some of these objectives will be met by the present invention.
2. Description of the Background Art
U.S. patent application Ser. Nos. 10/412,714 and 10/637,713, previously incorporated by reference, describe apparatus and methods for delivery of multiple distributed stents. U.S. Pat. Nos. 6,485,510 and 6,258,117 to Camrud et al. describe segmented stents with breakable connections between the segments. U.S. Patent Application Publication No. 2002/0156496 (inventor Chermoni) describes a catheter for carrying stents including a stent positioner. U.S. Pat. No. 6,143,016 to Beam et al. describes a stent delivery sheath. U.S. Pat. No. 5,807,398 to Shaknovich describes a shuttle stent delivery catheter. U.S. Pat. No. 5,571,086 (Kaplan et al.) and U.S. Pat. No. 5,776,141 (Klein et al.) describe an expandable sleeve for placement over a balloon catheter for the delivery of one or two stent structures to the vasculature. U.S. Pat. No. 5,697,948 to Marin et al. describes a catheter for delivering stents covered by a sheath. Patent application serial numbers 2003/0139797 (Johnson) and 2003/0114919 (McQuiston) describe covered segmented stents.